The recent appearance of this latter type of reactive armor, made up of alternating explosive layers, called active protection, and layers of dense armor, for example, steel, glass or composite and affording a greater measure of protection than is obtained with main armor, has led to the development of warheads comprising shape charges operating sequentially from front to rear, and which are called "tandem mounted". This type of configuration proves very effective in the following conditions:
1) the first charge to detonate, called the forward charge, must be sufficient to destroy all overprotection; PA1 2) the time delay between action of the two charges must be long enough to allow the interference capability of the active protection to be inhibited; and, finally, PA1 3) detonation of the forward charge must have no or little damaging effect on the destructive capability of the main charge, which activates subsequent to the forward charge.
In fact, conditions 1 and 3 are mutually contradictory: if the destructive capacity of the forward charge is increased, then, especially if the lapse between detonation of the two charges is too long (for example, more than 0.5 ms) the inevitable result will be an alteration of the main charge's performance.
French Patents Nos. 2,559,896 and 2,581,749 illustrate this contradiction: they describe a low effectiveness forward charge making possible a long time lapse without excessive additional weight whereas French Patent No. 2,552,869 discloses a high-performance forward charge combined with a short time lapse and/or massive protection.
For use against multi-layer armor, other warheads are known which comprise shape charges which act in succession, but from back to front, as illustrated, for example, by U.S. Pat. No. 4,004,515. This type of configuration implies the use of forward shape charges in sections which are only slightly effective because of damage done to them by rear charges which are initiated first, despite complex tubular structures whose purpose is to guide the rear charges' jets through the forward charges' liners.